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SR10 Low FPS


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#1 Gregory Merrill

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Posted 03 July 2014 - 07:10 PM

Hello, recently I found a problem with the fake bolt in my sr10 and I only found this problem after I am assuming it was like this for the month i hadn't used it.The problem is that the metal bent and had shoved my hopup chamber into the outer barrel, which I am guessing compressed the spring on top of the hopup. I went to test shoot it and discovered that I have major compression issues, like cant even break one layer of cardboard. I removed the bolt and still had the problems. Bucking is not torn, gearbox is still great(haven't fired more than 5k rounds through it). How could I confirm this as the problem and how can I fix it if it is the issue,
Thanks


Pics:    http://imgur.com/a/brVLU

Edited by Gregory Merrill, 03 July 2014 - 07:37 PM.


#2 StealthTaskForce

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Posted 03 July 2014 - 07:16 PM

Make sure the nub in the gearbox is seated correctly. If it's lopsided, it could cause drastic decrease in fps due to added pressure. That would require taking off the hop up assembly from the inner barrel and then taking apart the assembly. If everything there is fine, look for other signs of wear on other areas around the bolt. If it was bent enough, it could cause something else to break that might not be as obvious. When my bolt was bent on my Mod 2, every time it slammed home it would adjust my hopup because it made contact with the adjustment wheel. So check to make sure it isn't touching anything else, and then as always, pictures do help for the more experienced of us (not me lol) :thumbsup:

#3 Gregory Merrill

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Posted 03 July 2014 - 07:29 PM

View PostStealthTaskForce, on 03 July 2014 - 07:16 PM, said:

Make sure the nub in the gearbox is seated correctly. If it's lopsided, it could cause drastic decrease in fps due to added pressure. That would require taking off the hop up assembly from the inner barrel and then taking apart the assembly. If everything there is fine, look for other signs of wear on other areas around the bolt. If it was bent enough, it could cause something else to break that might not be as obvious. When my bolt was bent on my Mod 2, every time it slammed home it would adjust my hopup because it made contact with the adjustment wheel. So check to make sure it isn't touching anything else, and then as always, pictures do help for the more experienced of us (not me lol) :thumbsup:
Yeah no signs of wear, nub is great, but I noticed when I slide the hopup assembly into the upper receiver and seat it all the way down, it doesn't bounce back up but stays down, maybe the spring is worn out?
PICS:   http://imgur.com/a/brVLU

Edited by Gregory Merrill, 03 July 2014 - 07:34 PM.


#4 StealthTaskForce

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Posted 03 July 2014 - 07:33 PM

Do you have to kind of shove the inner barrel into the outer barrel? Because you shouldn't have to. But if it easily slides in and out and still doesn't bounce back up, then yeah the spring is probably worn down. And I'm not sure, but that will probably cause you to lose air pressure, thereby lowering your fps. Gcw, feel free to correct me if I'm wrong lol

#5 Gregory Merrill

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Posted 03 July 2014 - 07:36 PM

It's pretty easy to slide in and out yeah, I saw someone say something about the spring being a really easy fix but that was a while ago.

#6 StealthTaskForce

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Posted 03 July 2014 - 08:10 PM

The spring actually doesn't look all that worn down to me.. It doesn't look compressed or anything. But you said it didn't bounce up again after you inserted it?


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#7 Gregory Merrill

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Posted 04 July 2014 - 12:27 AM

View PostStealthTaskForce, on 03 July 2014 - 08:10 PM, said:

The spring actually doesn't look all that worn down to me.. It doesn't look compressed or anything. But you said it didn't bounce up again after you inserted it?


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Yes the hopup goes down into the outer barrel and doesn't move from there, so either it's getting stuck, the spring is worn, or the place where the spring pushes off of is missing / farther down

#8 gcw360

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Posted 04 July 2014 - 06:50 AM

Have any modifications at all been done to the gun?  Has it ever been taken apart?

The spring looks fine.  There could be some flash in the otter barrel that is keeping it from bouncing back.  Try this.  First fire the gun 3-4 times. Note: Do not look down the barrel for the next step!!! Take a pencil, and from the birdcage, gently push the inner barrel back towards the gearbox. Test the first shot, is it stronger?  If not, it's not the spring IMO.  If so, look in the outer barrel for any metal flash that might be restricting the inner barrel from moving.  This can be removed with a flat head screwdriver.

Next, look for any debris at the back of the upper receiver where the  hop-up rests when installed.  This can cause a loss of compression.  As can the bucking being non-stock or damaged.  Or, the hop-up isn't properly installed.

Once you have eliminated the hop-up, it's time to look for issues in the gearbox like:
  • Damaged piston
  • Damaged cylinder head
  • Damaged piston o-ring
There can be other reasons but those are the biggies to start with.

Hope this helps.

#9 Gregory Merrill

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Posted 04 July 2014 - 08:28 AM

I just tried what you said and the barrel did move back substantially (3/4 inch) and it felt stronger. I cracked the receiver open to check for metal flash and tried pushing on the hopup, it pushed back surprisingly, but no metal flash inside, how could I prevent it from getting "stuck" again?

#10 gcw360

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Posted 04 July 2014 - 10:38 AM

Look to see where the outer barrel touches the inner, most likely where the end piece screws onto the outer barrel.  At that point take a wide flat head screw driver and turn it against the metal.  See if anything comes off.  It should only be a little bit of metal but if it impedes the inner barrel that's all that is needed to mess with the inner barrel.  But something you wrote troubles me...3/4"  That seems crazy like excessive movement!!!

#11 Gregory Merrill

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Posted 04 July 2014 - 10:46 AM

Found it! After looking at diagrams and disassembling my RIS and Outer barrel I found a pin that was out of place that kept the outer barrel from rotating, added some tape to it to fill the hole and prevent movement as well as keep the pin in place, thanks for all the help!

Edited by Gregory Merrill, 04 July 2014 - 10:47 AM.


#12 gcw360

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Posted 04 July 2014 - 11:23 AM

So, the whole outer assembly was moving forward?  That would do it!!! Thanks for posting.  Now, I suggest you simply add a drop of blue locktite and take off the tape.  But that is up to you.  Thanks for posting

PS - Posting a pic would help others here.




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